Isocyanates preparation

Acyl aminimides have proved useful as surface-active and antimicrobial agents and as an intermediate for isocyanate preparation (50). 

Brzezinska KR, Curtin SA, Deming TJ (2002) Polypeptide end-capping using functionalized isocyanates preparation of pentablock copolymers. Macromolecules 35 2970-2976... 

A violent explosion occurred during vacuum distillation of 4-chlorophenyl isocyanate, prepared by Curtius reaction from the azide. It was found by IR spectroscopy that this isocyanate (as well as others prepared analogously) contained some unchanged azide, to which the explosion was attributed. The use of IR spectroscopy to check for absence of azides in isocyanates is recommended before distillation [1], Subsequently, the explosion was attributed to free hydrogen azide, produced by hydrolysis of the unchanged acyl azide [2],... 

Warning is given against dry distillation of the alkali salts as an isocyanate preparation. The decomposition is often explosive... 

In order to gain a better insight into these problems, a fundamental study of simple mono- and di-urethanes of the furan series was undertaken. This included the determination of their structure, properties and stability (35) and the mechanism and kinetics of their formation. The combinations investigated were furan alcohols and diols with aliphatic, aromatic and furanic isocyanates and the latter mono- and bis- derivatives with aliphatic and arylalkyl alcohols and diols. The furanic isocyanates prepared included 9 and those given below ... 

The isocyanate prepared in benzene solution (123, 124) consists, according to osmometric measurements, of a mixture of the dimer and... 

Direct Synthesis reaction of, 6 395 fluoride, 21 235, 237, 239, 249 homopolyatomic cations, 17 82 ion, stereochemistry, 2 40-41, 44-45 isocyanates, preparation, 9 158 properties, 9 157 isothiocyanates, properties, 9 177 mixed valence compounds of, 10 375-381 crystal structure of, 10 376 diffuse reflectance spectrum of, 10 380 structure of Pb," ion, 10 381 nuclear magnetic shielding, 22 224 organometallic compounds, 2 82, 88, 89 oxide, neutron diffraction studies on, 8 231-233... 

Eloy and Deryckere have applied their synthesis of isocarbostyrils (69HCA1755) to the preparation of thieno[2,3-c]- and thieno[3.2-c]-pyridines (Scheme 65) (70BSB301). Thermal-cyclization of 3-thienylvinyl isocyanate prepared from the corresponding azide (269) by Curtius rearrangement yields thieno[2,3-c]pyridin-7-one (270), which is transformed to (259) following usual methods. 

Preparation of phosphorus ylides Elimination of nitrous acid Steric control of elimination reactions. Mdol condensation Rearrangements Reactions with aryl isocyanates Preparation of carboxylic acid chlorides Synthesis of macromolecules... 

Phenoc-protected amines were prepared in two ways. The first involved the reaction of an amino acid with the oxime carbonate 5 to yield 6 as shown in Scheme 7. The second method consisted of reaction of the a-hydroxy ketone with an isocyanate. Preparation of the phenacyl chloroformate was attempted, resulting in a cyclic carbonate which was inert to amines. 

The chemistry of aminimides has been reviewed elsewhere (Ref. 204, 205) and the chemistry of dimethyl amino isocyanate, prepared in the form of dimer (d) through a phosphoramide synthesis, studied (206). 

Reaction of an ynamine with an isocyanate (prepared in situ by rearrangement of an azide) leads to the formation of a pyridine ring [2333]. Intramolecular cyclization of an (isothiocyanatoethyl)benzene is effected by heating with triethyloxonium tetrafluorotorate or with PPA. With the former, the salt may be converted into its free base with aqueous carbonate [2843]. Photolysis of a vinyl isocyanate (formed in situ) gives a good yield of a 1-isoquinolinone. The corresponding isothiocyanate ion produces a mixture of products of which the... 

Then yields of isocyanates prepared by such routes can be good. Romano made 1,6 diisocyanatohexane from hex-amethylenediamine in an overall yield of 77% using a sodium methoxide catalyst to form the intermediate bisurethane.21 (Enichem is putting up a pilot plant to study the commercialization of such processes.22) Ookawa et al. ran a similar conversion to produce the diisocyanate in 92.5% yield with 1.2% monoisocyanate, which could be recycled to the process (2.6).23... 

The cyclotrimerization of monofunctional isocyanates, preparation and properties of polycocyclotrimers based on isocyanates were investigated. 

The sulfonyl component of propoxycarbazone-sodium (2) is an integral part of several commercial sulfonylureas [21]. Technical procedures exist for sulfonyl isocyanate preparation starting from saccharin (Scheme 2.6.5) [22, 23]. 

An attempt to synthesise 2,2,2-trinitroethyl isocyanate was successfully completed, and the methodology thus established was developed into a general isocyanate preparation (Scheme 49). ... 

The following specific precautions should be taken in the handling of isocyanates. In general, the handling of isocyanates in open vessels should be avoided as much as possible. For example, liquid isocyanate preparations should be transferred to vessels by pumps or by vacuum technique. Methods of dip-leg transfer by means of air pressure applied to a supplier s drum are not acceptable since escapes of vapour may occur. Fully enclosed systems of handling should be used wherever practicable. 

Aromatic Isocyanates Aryl isocyanates prepared with phosgene... 

Poly substituted aryl isocyanates 236 and 238 were obtained with diphosgene in dioxane, ethyl acetate, or toluene from 3-fluoro-4-methoxyaniline 235 [164] and 3-amino-2,6-dichloro-4-fluorophenyl methyl carbonate 237 [165], respectively. Table 4.8 summarizes the reported substituted aryl isocyanate preparations with diphosgene. 

Tab. 4.8. Substituted aryl isocyanates prepared with diphosgene.

Tab. 4.9. 4-Substituted phenyl isocyanates prepared with triphosgene [178].

---